The web consensus seems to agree that neither is the right answer: Go with reusable cloth bags. They're more durable, won't fill up landfills (or gutters), and the energy spent making them -- an aspect of the debate sometimes overlooked -- won't be wasted on one-and-done use.
Which seems straightforward. But I confess that I never use reusable bags and when I'm at the store, I rarely see others using them. How do we incentivize the use of reusable bags? New Hampshire's General Assembly has just passed a resolution to "encourage" consumers and retailers to go reusable. But I'm a skeptic that encouragement will do the trick -- for most people, good intentions and sobering statistics about paper and plastic bags don't seem to work.
So what good ideas are out there? Some stores offer "reward points" for reusable bags. Other stores, it seems, charge for non-reusable bags, which seems the strongest incentive to my mind. But is that a good idea with food prices already climbing? Would those stores that do charge appear "greedy fat cats" for charging for grocery bags (what if they donated the surcharge to some nice cause)? Would a nickel be enough to dissuade many people from using paper and plastic?
What other ideas are out there? More importantly, what works?
